One of the oldest homogeneous catalytic reactions of olefins is hydroformylation, the addition of CO and hydrogen to produce aldehydes. The reaction is carried out commercially utilizing a suitable catalyst, e.g., cobalt catalyst, and may be illustrated as follows: ##STR1## Alcohols may incidentally be formed as a result of hydrogenation.
The cobalt catalysts which have been used in hydroformylation reactions include HCo(CO).sub.4 and Co.sub.2 -(CO).sub.8. However, these carbonyls are relatively unstable and volatile. Hence, they are difficult to separate from the reaction products for the recycling of catalyst. Additionally, these compounds have limited selectivity for the desired linear aldehydes and alcohols. Furthermore, these catalysts require high pressures, e.g., 200 atmospheres, at temperatures of about 120.degree.-140.degree. C. These severe reaction conditions impose economic penalties for high-pressure reactor investment and for construction and operation of the gas compressor. These problems have resulted in the development of phosphine modified cobalt catalysts and rhodium catalysts to give higher yields of linear aldehydes under mild conditions.
The phosphine modified cobalt catalysts are typified by the component HCo(CO).sub.3 (PBu.sub.3). While this tributyl phosphine catalyst is more stable and may be used at lower pressures, e.g., 100 atmospheres, it is less active for hydroformylation than HCo(CO).sub.4 and yields an inferior rate even at elevated temperatures, e.g., 180.degree. C. It is, however, much more active as a hydrogenation catalyst. As a result it has the further limitation that some olefin is lost through hydrogenation to alkane.
Rhodium analogs, e.g., HRh(CO) (PPh.sub.3).sub.3, of the phosphine modified cobalt carbonyls have been prepared and utilized successfully as hydroformylation catalysts. While this compound is more stable than HCo(CO).sub.4 it requires excess phosphine ligand to stabilize it during product distillation and catalyst recycle. It is, however, advantageously selective toward the formation of a higher yield of the more desirable linear aldehydes. Despite its advantages (high selectivity and low-pressure operation), the high cost of rhodium inventory and recycle has limited its use.
There is a need for a low cost, stable, hydroformylation catalyst which has high selectivity and results in good yields at low pressures, e.g., 100 atmospheres or less. Although a large number of metal carbonyl compounds have been prepared, none other than the cobalt and rhodium compounds discussed above have been disclosed as being effective hydroformylation catalysts. Illustrative of the known metal carbonyl compounds are those disclosed in the prior art discussed below.
U.S. Pat. No. 3,824,221 discloses metallated polymers and copolymers where the polymer may be styryl phosphine and the metal is selected from Groups IVA to VIII and IB of the Periodic Table of the Elements. The metallated polymers are said to be hydroformylation catalysts.
Similarly, U.S. Pat. No. 4,111,856 discloses resin-metal compound complexes useful as hydroformylation catalysts. The metal can be transition metals including nickel, cobalt and rhodium. Copper is also disclosed as a suitable metal. These resin-metal compounds may contain one or more functional groups such as amine, carbonyl or phosphine. Neither U.S. Pat. No. 3,824,221 or 4,111,856 disclose bimetallic compounds containing copper.
U.S. Pat. No. 3,959,385 discloses hydroformylation catalysts comprising carbonyl complexes of metals in Group VIII of the Periodic Table of the Elements, the complexes being modified by trisubstituted organic phosphines which contain at least one carbonyl group.
Other metal carbonyl complexes useful as hydroformylation catalysts are disclosed in U.S. Pat. Nos. 4,259,530; 4,292,126 and 4,334,042. The metals suitable for use in the catalysts include cobalt and rhodium.
Certain bimetallic carbonyl complexes containing phosphines or amines are taught in the literature. For example, the CA Registry discloses a compound of the formula EQU (Ph.sub.3 P)CuIr(CO).sub.3 (PPh.sub.3)
designated as CAS Registry No. 81506-93-6. Other bimetallic complexes which contain copper are disclosed in an article by Kuyper et al., "Metal-Metal Bonded Triazenido Compounds", J. Organomet. Chem. (1975), 96(2), 289-99. The compounds disclosed include: EQU (Ph.sub.3 P).sub.2 (CO)RhCu(L')Cl; (Ph.sub.3 P).sub.2 (CO)RhCu(DMT)I; (PhMe.sub.2 P).sub.2 (CO)RhCu(DMT)Cl; EQU (Ph.sub.3 P).sub.2 (CO)IrCu(L')Cl; (Ph.sub.3 P).sub.2 (CO)IrCu(DMT)I; (PhMe.sub.2 P).sub.2 (CO)IrCu(DMT)Cl and EQU (Ph.sub.3 P).sub.2 (CO)IrCu(O.sub.2 CCF.sub.3).sub.2
where L'=dimethyl triazene (DMT); methyl (p-tolyl) triazene (M.sub.p TT) and di(p-tolyl) formanidine (D.sub.P TF).
Compounds of the structure ##STR2## wherein M, Y, R and R' are: Rh, N CH.sub.3, CH.sub.3 ; respectively or
Ir, N, CH.sub.3, CH.sub.3 and phosphines are PPhMe.sub.2 ; PA1 Ir, N, CH.sub.3, tolyl PA1 Ir, CH, tolyl, Et.
are disclosed by Van Vleet et al in J. Organomet. Chem (1979), 182(1), 105-15. The aforedisclosed compounds of Kuyper et al have similar structures.
Related copper-cobalt complexes include (Ph.sub.3 P).sub.3 CuCo(CO).sub.3 (PBu.sub.3) and (Triars)CuCo(CO).sub.4 where Triars is [(CH.sub.3).sub.2 AsCH.sub.2 ].sub.3 CCH.sub.3. None of these copper compounds have been said to exhibit catalytic activity in hydroformylation reactions. See for Example "Metal-Metal Bonds v. Complexes Containing Copper-Silver-Metal Linkages," A. S. Kasenally et al, J. Chem. Soc., 1965 (Oct.) 5331-6 and "Synthesis of Transition Metal Derivatives of Magnesium," G. B. McVicker & R. S. Matyas, J. Chem. Soc., Chem. Commun., 1972, (17) 972.
The art discloses certain copper-cobalt carbonyl complexes of the formula "bipyCuCo(CO).sub.4 ].sub.n where "bipy" is bipyridyl. See "Preparation, Structure and Reactions of New Complexes Containing Copper or Silver Bonded to Transition Metals", P. Hacket and; A. R. Manning, J. Chem. Soc., Dalton Trans. 1975(15) 1606-9. While this compound is taught to be a polymer it is these inventors belief that the compound is in fact bipyCuCo(CO).sub.4.